a more versatile engine than the PT6 where none of this is possible
Mate, dunno where you got your info but yer wrong. PT6 on the B200 can certainly run avgas and mogas up to 150hr total between HSI. The exact fuels are listed in the POH.
Bloody thing will run on cooking oil if you want to.
There are good, well equipped and long TTR mid-1980s SKAs (same vintage as the MU2 etc) to be had for $400-500K.
As for the original question, Conquest is prob the quickest from my limited RH seat time in one, Commander is undoubtedly the noisiest.
Have you considered the least expensive of the lot - the Cheyenne? A PA42-720 Cheyenne III or IIIA is a pretty good performer, load hauler, long range and would be the least expensive of all these to buy and run - expense being a relative term in kero-burners. Or if you REALLY wanna haul, the PA42-1000, with Garretts. Niiice.